Power shifting multi-step transmissions



April 25, 1961 KELLEY 2,981,126

POWER SHIFTING MULTI-STEP TRANSMISSIONS Filed Dec. 25, 1952 9 Sheets-Sheet 1 ESnDe-nlvr 33 I @Rorngs.

April 25, 1961 Q KELLEY 2,981,126

POWER SHIFTING MULTL-STEP TRANSMISSIONS Filed Dec. 23, 1952 9 Sheets-Sheet 2 Inventor 675 /6! ifi/[g Attorneys April 25, 1961 O KELLEY 2,981,126

POWER SHIFTING MULTI-STEP TRANSMISSIONS Filed Dec. 23, 1952 9 Sheets-Sheet 5 Inventor Attorneys April 25, 1961 O KELLEY 2,981,126

POWER SHIFTING MULTI-STEP TRANSMISSIONS Filed Dec. 23, 1952 9 Sheets-Sheet s w ks? Inventor Attorneys April 25, 1961 Q KELLEY 1 2,981,126

POWER SHIFTING MULTI-STEP TRANSMISSIONS Attorneys April 25, 1961 0. K. KELLEY 2,981,126

POWER SHIFTING MULTI-STEP TRANSMISSIONS Filed Dec. 25, 1952 9 Sheets-Sheet 6 REVERSE 51 067(5)? lzfl Inventor 67/ 26! if'if/fgy I v b mg-W rne CZ 0761/ Arte April 25, 1961 Q KELLEY 2,981,126

POWER SHIFTING MULTI-STEP TRANSMISSIONS Filed Dec. 23, 1952 9 Sheets-Sheet '7 JUMP Inventor Attorneys April 25, 1961 0. K. KELLEY POWER SHIFTING MULTI-STEP TRANSMISSIONS 9 Sheets-Sheet 8 Filed Dec.

llllllllllllllilllll i IIIIIIIIIIIIIIHIIII V/iflez W i ATTORNEYS I April 25, 1961 0. K. KELLEY POWER SHIFTING MULTI-STEP TRANSMISSIONS Filed Dec. 25. 1952 9 Sheets-Sheet 9 IENTOR ATTOFNEYS 2,981,126 I rowan SHIFTlNGMULTI-STEP TRANSMISSIONS Filed Dec. 23, 1952, Ser. No. 327,563

29 Claims. (Cl. 74-73'1) This invention relates to improvements in transmissions and, more particularly, to improvements in power shifting multi-step transmissions.

In internal combustion engine driven vehicles, it is customary to, provide transmissions interposed between the engine and the driving axle of such character that changes in gear ratio can be made over a relatively wide range. In cases whert the desired range is very wide and maxi mum performance is of great value, it becomes necessary to provide mechanisms for obtaining a progressive change in gear ratio in a great number of steps, with only a small difference between each successive step. Transmissions for this purpose involving many gear ratios necessarily become quite cumbersome and, if the gearing is arranged in tandem fashion, the overall construction of the gearing and the complication of controls for the multitudinous shifts present a major technical and economic problem. v

An object of the present invention is to provide a transmission accomplishing the objectives of the diflicult-toobtain multi-step transmission by using two or more relatively simple transmissions, each containing only a few ratio change steps of larger ratios.

Another object of the invention is to provide a transmission, as just described, suitable ,for handling higher horsepower engines by using two or more transmissions originally designed for handling only smaller power plants. 7

Another object of the invention is to provide automatic transmission in which the components are so arranged as to occupy a relatively short space between the engine and the driven axle.

Another object of the invention is to provide a transmission, as hereinbefore described, in which an oversized fluid coupling or hydraulic torque converter is interposed between the engine and the mechanisms, such fluid coupling being modulated by centrifugally'acting plugs which impede the flow of fluid at low speed of rotation, thus eliminating creep.

In carrying out the foregoing and other objects of the invention, a transmission incorporating the same may be composed of two or more parallel plural step ratio change mechanisms of any of a number of well-known types. For example, in the described embodiment of the invention, use is made, in each of the mechanisms, of a well-known commercial automatic transmission of four forward speeds and a reverse. Each of these mechanisms has its own hydraulic controls for causing automatic change of speed ratio in response to torque demand, as represented by throttle action, and vehicle speed, as represented by fluid pressure from its governor driven by its output shaft. in this particular arrangement use is made of a single fluid coupling serving the two mechanisms, the pump of which is driven directly by the flywheel of the engine, and the turbine or mnner of which is connected through a planetary gear arrangement to the respective inputs of the two transmissions in such fashion thatthese inputs n ted States Patent are differentially driven. The output shafts of the two transmissions are geared together so that the output shaft of one of them runs faster than the other.

If the two transmissions have equal automatic shifting mechanisms, it is obvious that the faster running transmission will upshift automatically at a lower vehicle speed than the slower running transmission. The diiferential drive to the inputs of the two transmissions accommodates this action, affecting the engine speed only by 0 one half of the ratio change of the shifting unit and affecting the overall drive ratio of the combination by only one half of the same ratio change.

It is evident that if three of these units were used in a similar difierential arrangement, the effect of one units shifting would be only one third in overall ratio. Extremely small ratio changes can thus be obtained by the use of several transmissions in this arrangement.

Parts of the hydraulic controls for these individual mechanisms are operated in unison, preferably in response to throttle action, while other parts thereof operate in response to throttle action associated with output shaft speed as represented by the fluid pressure of the individual governors driven by these output shafts. The results of this interconnection and association is that the respective mechanisms operate to change gear ratio independently, one after the other, so that, due to the difference in output speed, determined by the ratio of connection between the output shafts, the change in gear ratio in the mechanisms will take place at staggered intervals, one relative to the other. Thus, with two mechanisms, each having gearing providing four forward speeds, it is possible to obtain, due to their coaction, seven forward speeds with overall drive ratio steps only half as large as the steps in each unit. A similar result would be obtained if the two units had their outputs geared at equal speeds, but their governors geared differently. Another way would provide equal speeds of the two units including the governors but with different weights of the governors to make them act as if they were running at different speeds. Still a further way could make use of a single governor and impose design changes in the controls of one unit so as to make it shift at lower vehicle speeds than the other unit.

Furthermore, additional speed ranges can be obtained by appending to the output shaft of this parallel drive an additional planetary unit which can provide either a reduction ratio or a direct drive condition. With this additional unit, it will be evident that the operator of the vehicle may have a choice of fourteen possible speed ratios.

The differential drive to the two units divides the engine torque into two. Thus each transmission works under loads and stresses like those imposed by an engine of only half the size. Commonly available smaller size automatic transmissions can thus be combined to serve much larger power plants without danger of overloading the mechanism. It is within the contemplation of the invention that the parallel mechanisms need not necessanily be limited to two but can be increased as may be desired, and the speed changes of each mechanism can be any desired number.

Other features, objects, and advantages of the invention will be apparent by referring to the following detailed description of the accompanying drawings, in which the reverse mechanism of one of the units and a part of the final gearing unit employed in the transmission,

Fig. 4 is an enlarged section showing a feature of construction of the fluid coupling,

Fig. 5 is a section of the manually operated valve for controlling the final unit of the transmission,

Fig. 6 is a section through the servo unit associated with the rear planetary of each mechanism,

Fig. 7 is a similar View of the servo unit associated with the front planetary of each mechanism,

Fig. 8 is a section through a part of the control valves of one of the mechanisms,

Fig. 9 is a similar section through another part of the valve body showing the various elements mounted therein,

Fig. 10 is a section through one of the governors,

Figs. 11 and 11a together constitute a schematic diagram showing a part of the hydraulic'mechanisrn and its association with the various operating parts,

Fig. 12 is a diagrammatic representation of another embodiment of the invention, and

Figs. 13, 14, 15 and 16 are diagrammatic representations of other embodiments of the invention.

Referring to the drawings, the gearing and other mechanical parts of the transmission have been illustrated in Figs. 1, 2 and 3. Referring particularly to Fig. l, 20 indicates the flywheel construction driven by the engine (not shown) of the vehicle. This flywheel construction is connected to the pump or driving element 21 of a fluid coupling of well-known type. The turbine or runner 22 of the coupling is connected to a planetary carrier 24 to cause rotation of the carrier and its planet gears therewith. The sun gear 25, associated with the planets mounted on the carrier 24, is secured to or forms part of a sleeve shaft 26 which is extended in steps to the ring gear 27 of the front driving unit of the upper plural step ratio change mechanism incorporated in this invention. The ring gear 28, associated with the planets of carrier '24, is attached to a sleeve shaft 29, which extends in steps to a gear 39 connected through an idler indicated by dotted lines 31 to another gear 32, the shaft of which is extended in steps to the ring gear 27' of the lower plural step ratio change mechanism employed in this invention. Pump 33 is connected to be driven by the pump 21 of the fluid coupling. This pump may be of any well-known type but preferably is of the variable capacity type, particularly as described in the pending application of Herndon et al., S.N. 153,342, filed April 1, 1950, for Variable Capacity Pump, now abandoned. The pump operates to deliver oil to meet variable demands at a pressure regulated within the pump.

Inasmuch as the upper and lower mechanisms, driven respectively by the ring gears 27 and 27' are of substantially identical construction it is believed that a more detailed description of the parts of one thereof will suffice.

The compound planetary gearing employed in each of these mechanisms is of generally well-known character consisting of a front driving planetary unit, a rear driving planetary unit, and a reverse planetary unit.

The front driving planetary unit, of which ring gear 27 is a part, also comprises the planet carrier 35, secured to or formed as part of intermediate shaft 36, and sun gear 37 mounted for rotation about the shaft 36.

Planet carrier 35, in addition to having planets mounted thereon, is extended into an annulus 38 upon which are slidably mounted a plurality of clutch plates 39. The sun gear 37 is, in effect, extended into a drum 40, the periphery 41 of which serves as a brake surface to be engaged by a brake band 42. A plurality of clutch plates 44 are mounted within the drum for sliding movement relative thereto and are compelled to rotate therewith by the engagement of one or more rods 45 with notches in the peripheries of the clutch plates. A clutch piston 46 is also mounted within the drum 40 for movement under hydraulic pressure to force the cooperating plates 39 and 44 together and against the resistance offered by a backing plate 47 for locking the sun gear to the planet carrier.

The intermediate shaft 36 is extended to a sun gear 50 of the rear drive unit, this gear being either secured to or formed as part of the shaft 36. Splined to shaft 36 is a member 51, the periphery of which serves to retain, for sliding motion, a plurality of clutch plates 52. Inasmuch as the member 51 is splined to the shaft 36, it must of necessity rotate in unison with the sun gear 50. The ring gear 54 is mounted within a drum 55, the periphery of which, as indicated at 56, can be engaged by a brake band 57 which, when applied, serves to prevent rotation of the ring gear. Drum is so shaped as to retain one or more rods 58 which serve to locate and to compel rotation of a plurality of slidable clutch plates 59. A piston 60 is mounted in the drum 55 for applying pressure to force the plates 52 and 59 together between plate 61 and buttress 62 thereby to lock sun gear 50 and ring gear 54 together. Planet carrier 64, the planets of which mesh with the sun gear 50 and ring gear 54, is secured to or formed as part of output shaft 65. The ring gear 54 is effectively connected to a sleeve shaft 66 by a washer-like member 67, attached near its extremity to the drum 55 and having its central aperture splined to the shaft 66.

The reverse planetary unit has its sun gear 68 secured to or formed as part of the sleeve shaft 66 and meshes with the planets of carrier 69, which is secured to the output shaft for rotation therewith. Carrier 69 is connected to output shaft 65 in the same manner that carrier 69 of the lower mechanism is connected to the output shaft 65 thereof. This arrangement is shown clearly in Fig. 3 wherein it will be seen that the carrier 69' is splined to output shaft 65. The ring gear 70 of this unit has a hub rotatable about the extension of the carrier and also has a cone 71 extending angularly outwardly therefrom. Another cone 72 is attached to the housing for this transmission and a piston 74 has a coned surface 75 thereon which can engage the cone 71 and force it into engagement with cone 72, thereby grounding the ring gear or locking it against rotation.

The output shaft 65 terminates in a gear which may be integral therewith or may be secured thereto in any fashion for concurrent rotation. Gear 80 is connected by an idler 81, shown in dotted lines in Fig. l, with a gear 80' which is driven by the output shaft 65 of the lower mechanism. The relative size of the gears 80 and 80' is predetermined so that rotation of the shaft 65 will be at a definite ratio to the rotation of shaft 65', with the ratio between the shafts being such as to fit the conditions for which the transmission is to be used. For example, in the described embodiment of the invention, a ratio of 1.25 to 1.00 is selected since that is about half the average ratio step of the two parallel four speed transmissions used; this will then provide seven reasonably equal speed ratios due to the independent type of governor control selected, as previously described.

It will be understood that the elements combined to form the lower unit are substantially identical in character with those described in connection with the upper unit, and hence the same reference characters with the addition of a prime have been used to identify these corresponding parts.

By reference to Fig. l and also to Fig. 3, it will be seen that the output shaft 65 of the lower mechanism has been extended to serve as a common output shaft for both mechanisms. This extension is of such length as to permit the addition of a reduction unit to the mechanisms. This unit comprises a sun gear secured to or formed as a part of the extension of shaft 65', a planet carfier 86 connected to a propeller shaft 87, and a ring gear 88. Secured to shaft 65, for rotation with the sun gear 85, is a plate annulus 89, to the periphery of which are slidably secured a plurality of clutch plates 90. The ring gear 88 has an extension 91 secured to a-drum;like;member- 93 by bolts 93', :within whichfa're slidablymounted, for rotation therewith, a pluralityof plates 92. A piston 94 is secured within the drumto compress the plates 90 and 92 to effectively lock the ring gear to the sun gear. The drum 93 has splined to the periphery thereof a ring 95 from which extends a cone 96. Cooperating with cone 96 are the cone surface 97, attached to the housing, and the cone surface 98 of a piston 99 which can be moved under hydraulic pressure to cause engagement of the cone 96 between the surfaces 97 and 98, thereby to lock the ring gear to the housing or, in effect, to ground the same. The splined connection between the ring 95 and the drum 91 permits such movement of the ring and the cone as will be necessary for this engagement, while a wavy spring 100 serves to move the cone 96 away from surface 97 when such locking is not desired.

Oil seals have been shown at various points through the entire mechanism to prevent leakage at these points which might interfere with proper operation of the mechanism. Inasmuch as the use of seals for this purpose, and also the use of various lubrication channels, are all well known to the art, a complete illustration and description of these parts does not seem necessary.

Referring to Fig. 4, an enlargement of the cross-section of the fluid coupling has been shown. It will be noted that a cage 101 is attached to the pump 21 for rotation therewith. A number of plungers 102, which can slide in the bore provided by the cage, normally are spring pressed toward the inner surface of the pump by springs 104, part of which surrounds stationary pegs 105 and part of which fits within the hollowed-out plungers. When the pump is stationary or rotating at a relatively low speed, the springs 104 are of such strength as to maintain the plungers in the position shown both in Figs. 1 and 4. However, when the pump is rotated at such a speed that centrifugal force will overcome the strength of springs 104, the plungers 102 are moved radially outwardly until they are retained substantially within the cage. It will be understood that a considerable number of plungers so constructed are mounted about the pump, the purpose of these plungers being to obstruct or impede liquid flow from the turbine to the pump so that at low pump speeds coupling action is effectively prevented, with the result that parts driven by the runner have practically no torque applied thereto, and creeping of the vehicle at idling speed is prevented.

In Fig. 5 a valve body of the type associated with the last unit from which the propeller shaft extends has been shown. Body 110 has a bore 111 therein which is provided with an enlargement 112; a second enlargement 114 connected to the outlet conduit 115; enlargement 116 connected by passage 1 17 to chamber 118 and enlargement 119 connected to conduit 120. The purpose of these various conduits will be described in detail in the explanation of the operation of the entire mechanism. The valve member 121, slidable in this bore 111, has a plurality of indentations 122 near the lower end thereof which can be engaged selectively by one or more springpressed balls 124. This valve member also has spaced lands '125 and 126. The lower end of the valve has a groove 127 therein, to be engaged by a pin 123 at the end of a crank arm 128, rotatable about a shaft 129 for imparting movement to the valve within the bore.

The body 110 also has a bore 1'25 therein, restricted as at 126', 127' and 128'. The space between restrictions 126' and 127' is connected to a conduit 129', while the space between restrictions 127' and 128' is connected to a conduit 130, also connected to the space defined by the restriction 128'. A valve member 131 has a collar 132 thereon and is provided with-lands 134 and 135, and has spring 133 surrounding it below collar 132.

Mounted within the chamber 118 is a valve seat 140, against which is seated a valve 141 in the nature of a multi-cornered disk, the corners of which center-the valve within-the-boreof the chamber 118, but atthe same time the configuration is such that, when the disk is seated against the member 140, passage of oil in either direction is prevented. For example, the disk valve member 141 may be of flat triangular shape so dimensioned that the points or corners thereof will retain the disk in sliding engagement in the opening 118, while the solid center part thereof serves to close the seat 140. Member 141 is normally held in seated condition by spring 142 pressing thereagainst and surrounding a peg 144. An outlet conduit 145 extends to an accumulator 146, the function of which willbe described later.

A second-chamber 147 has a check valve member 148 mounted therein and is normally held against movement in one direction by a spring 149. Chamber 147 is connected to chamber 118 by passage 150; is connected to a conduit 151; and also has the end thereof beyond the valve-148 connected to one of the enlargements of the bore 125' by a passage 152. The purpose of describing this mechanism in the foregoing detail in connection with Fig. 5 is merely to describe the parts in a showing larger than the diagrammatic showing of Fig. 11, but the operation of these parts will become apparent in the description of Fig. 11.

Fig. 6 is an enlarged showing of the servo which operates to apply and release the band or brake 57 on the rear drive unit described in connection with Figs. 1 and 2. The servo comprises a housing having two chambers 155 and 156. Chamber 155 has an operating rod 157 extending therefrom, which rod is secured to a piston 158. Piston 158 is spring-pressed to the left by springs 159 and 160. Chamber 156 has extending therefrom into chamber 155 a rod 161 which is hollowed out and apertured to permit the passage of oil from the interior of the first chamber into the interior of the second chamber.

Rod 161 is secured to piston 162, normally forced to the left by springs 164 and 165. Conduit 166 is in communication with the interior of chamber 155 to the left of piston 158, while a branch 167 from this conduit is in communication with the chamber 156 to the left of piston 162. Another conduit 168 communicates with the interior of chamber 155 within the space formed as shown, whereby fluid can be introduced into this space to force piston 158 to the left. It will be noted that fluid so acting also passes through the hollow rod 161 into a space in the second chamber to force piston 162 also to the left. Rod 157 cooperates with linkage 157 to apply the band 57 to drum surface 56 in conventional fashion. The operation of this servo will be better understood in the detailed description which will appear later.

Fig. 7 is an enlarged showing of the servo utilized for applying and releasing the band or brake 42 associated with the first driving planetary unit described in Figs. 1 and 2. The servo of Fig. 7 is constructed to provide a chamber 170 through one end of which extends a rod 171 secured at the other end to a piston 172. This rod is hollowed out as shown for the passage of fluid from a zone adjacent piston 172 to another zone adjacent a second piston 174, also attached to the rod 171. A third piston 175 is secured to the rod 171 intermediate the pistons before mentioned. A combined partition, spring seat and guide 176 is mounted within the chamber. Springs 177 and 178 cooperate to move the rod 171' inwardly of the servo away from the drum 41 and thereby to relieve band pressure on the drum in the absence of fluid pressure in opposing direction. Conduit 180 is connected to the housing to admit fluid thereinto to act against piston 175, and conduit 181 admits fluid to the housing to.act against one surface of piston 172 and, due to the passage in rod 171, also to act against the end surface of piston 174. Conduit 182 extends into a bore 184, in turn connected by line 185 to the opposite sides of piston 172. Valve member 186 is slidable in bore 184 and is held against rotation therein by a pin 187, extending through an elongated slot in the valve. A restricted passage 138 permits fluid to pass through the valve 186 from conduit 182 to the line 185 when the piston is in position to register the restriction with the proper openings. Another conduit 189 communicates wit-h the bore 184 below a land 1% of the valve 186. v

In Fig. 8 a part of the control valve body structure and valves mounted therein has been shown. Inasmuch as this type of structure is well known to the art, and the operation thereof follows more or less conventional lines, it is believed unnecessary to go into a detailed description of the exact construction of each valve, since the operation thereof will be apparent from the'operational description which will appear later. It is believed suffieient at this time to point out that the valve body has mounted therein the usual manual control valve 200 which has a plurality of lands thereon, and which fits for sliding movement in a bore having a plurality of ports. The manual valve can be moved under the control of the operator into any one of four positions which are denoted by the circles appearing adjacent the end of the valve. For example, the circle marked N is the position at which the valve will be located when the transmission is in neutral condi tion. The second position, marked F-1, which is the position of the valve in Fig. 8, is the driving range, i.e., the position for normal forward propulsion of the vehicle. The third position, marked F2, is indicative of the position of this valve when it is desired to operate the transmission in the lowest ratio available which will not dangerously overspeed the engine; it is intended that this position would be used, for example, to produce a maximum of downhill engine braking and to prevent excessive ratio changing or hunting when operating in certain hill or traffic conditions.

The fourth position, marked R, designates reverse position of the manual valve for insuring operation of the transmission to impart backward movement to the vehicle. In addition to the manual valve, use is also made of a throttle valve composed of parts 201 and 202 longitudinally separated by a spring 204 with the part 202 having a stem slidably guided in the part 201. The usual throttle actuator 205 serves to move the part 202 and, under proper conditions, the part 201. A compensator valve 206 and a double transition valve 207 are also provided and, in addition, a front valve 208 is included for certain specific functions when the transmission is in. reverse gear. Various ports are provided in the valve body, some intercommunicating internally of the body and some being connected to external fluid lines or to other parts of the valve structure, which communication can best be represented by lines which apparently extend outwardly of the body.

Another part of the control valve body has been shown in-Fig. 9 wherein three governor plugs 210, 211 and 212 are shown as being slidably mounted and are associated respectively with shift valves 214, 215 and 216. These shift valves in turn are in operative relation respectively with regulator plugs 217, 218 and 219. Springs of various strength are interposed between the respective shift valves and their associated regulator plugs. It will be observed that the valves and plugs are mounted for sliding movement in bores provided with ports, some intercommunieating with other ports in the body, some communicating with external fluid lines, and some being connected to exhaust, the latter being marked Ex. The flow of fluid in this valve body will be better understood by the detailed operational explanation appearing later.

An enlarged illustration of one of the governor used in this invention has been shown in Fig. 10. The governor is of well-known type, and hence it is believed that a brief description thereof will suflice.

The body of the governor is provided with a bore in which a valve member 225 can reciprocate, being forced outwardly by centrifugal force acting on the weight 226 secured to the end of the valve member. It will be noted that this member 225 has portions of different diameters which can operate to close or open ports formed in the valve body. A similar member 227 is also mounted for reciprocation in the body and has a weight 228 at the outer end thereof, which weight is lighter than the weight 226. Fluid can be introduced to the body through the line 229 which is branched as at 230 and 231 in such fashion that fluid can be introduced to ports associated with the respective valve members and their weights. Normally, when the governor is at rest, the larger ends of the members 225 and 227 are in close proximity to each other, with the weights 226 and 228 retracted.

As the body is rotated, centrifugal force tends to move the weights outwardly and, since the weight 226 is heavier than weight 22 8, its outward force is larger. At rest, the port communicating with line 230 is closed by the smaller part of member 225, but when this member is moved radially outwardly this port is uncovered so that fluid enters the space between the large and small parts of the valve member. Due to the difference in diameters in these parts, when the oil delivered to the transmission reaches a pressure sufiieient to overcome the force exerted by weight 225, this pressure will force the valve 225 inwardly until some of the oil is exhausted through the branch of passage 234 and discharge port 236. This action of centrifugal force opposing oil pressure serves to regulate the outgoing volume of oil through the line 235 so that the pressure of the delivered oil is dependent upon the degree to which the valve assembly is moved radially outwardly. Thus the pressure of oil delivered by this part of the governor is responsive to the speed of rotation of the governor, and the governor is driven by the output shaft of the transmission mechanism, with the result that governor pressure, in this instance G-i pressure, varies in proportion to vehicle speed.

The same action occurs in the other part of the governor, with the result that fluid, entering the bore from line 231, passes therefrom through the passage 237 to the delivery line 238 and thence to the transmission mechanism. Since the weight 223 is lighter than weight 226, it follows that the pressure delivered from this part of the governor is proportional to vehicle speed but is less than 6-1 pressure, or in. other words, as output speed increases, 6-2 pressure is increased at a slower rate than is G l pressure.

It is believed that the sequential operation of the parts of the mechanism which have been described previously and in unassociated relation will be better understood by the following description of the functioning of the apparatus in the course of normal operation thereof. Since in most mechanisms of this type provision is made for preventing starting of the engine when the transmission is in other than neutral position, let it first be explained the mode of operation of the transmission in neutral.

Neutral The manual valve 200 (Fig. 8 and Fig. 11) is moved to the N or neutral position. When the engine is started and permitted to run at idling speed, the output thereof drives the pump 21 of the fluid coupling and also the variable capacity pump 35. As long as the coupling pump 21 is rotating at engine idling speed, the plungers 102 therein will remain in the position shown in Figs. 1 and 4; and due to the disposition of a plurality thereof about the pump, such fiow of fluid in the coupling as would cause rotation of the turbine 22 is reduced. The variable capacity pump '35 draws oil from the sump through line SL and, after any demands for high pressure oil are met, delivers oil to the fluid coupling through line CL to fill the same and also to supply lubricant throughout the mechanism. Oil is also delivered to the servo for the rear unit through the following path: from the outlet PL of pump 33 through line 301 to the manual valve body, but since land 250 of the manual valve in neutral blocks the port directly in line with 30.1, fluid is assume diverted to the branch 302 from which it passes through line 304 to the inlet 166 and branch 167 of the rear servo. This fluid, acting against pistons 158 and 162, draws rod 157 inwardly against spring pressure and thereby releases the band or brake 57 applied to the rear driving planetary unit. Land 251 of the manual valve in neutral position closes the port connected to line 308 so that fluid entering the valve through line 302 can only exit through line 304. Likewise in neutral position, land 252 of the manual valve closes the port connected to line 310 which constitutes a branch of supply line 301 so that line pressure is arrested at this land.

High pressure oil from the pump 33 is also supplied "through conduit 255 to a port in the valve body of Fig. 9,

and thence through passage 256 to a land on the shift valve 214, at which point it is arrested. It will be noted in Fig. 11 that the line 255 is extended to the lower mechanism to supply branches 301, 310, and also the line 151 which leads to the chamber 147 of the accumulator valve body (shown also in Fig. From thischamber the oil passes through the passage 150 to unseat valve 141, thereby supplying line 145 connected to the accumulator. Flow of oil through passage 117, also connected to the chamber118,'will be discussed later.

High pressure oil is also supplied through the pipe 229 to the governor associated with the upper mechanism and through pipe 229 to the governor associated with the lower mechanism. These two governors are driven respectively by the output shafts 65 and 65 of the two unitsand these output shafts are stationary in neutral position; hence, the governors are also stationary and there will be no output from either.

The clutch for the rear driving unit of the upper mechanism (composed of clutch plates 39 and 44) is exhausted through the line 309 which extends to the shift valve body (Fig. 9) and a port adjacent to the shift valve 215, at which location it is exhausted. Branch 308, which extends from line 309 to a port in the control valve body, is also connected to this same exhaust connection. The front clutch, i.e., the clutch having plates 39 and 44, is released or connected to exhaust through line 314, which is a branch of line 315, through line 315 which extends to the manual valve body adjacent to double transition valve 207, through the line 316 also atthc double transition valve to the shift valve body and thence to exhaust through a passageway in the body which terminates at the shift valve 214. The supply line for fluid to actuate the front servo to apply the band 42 consists of line 311 from the manual valve body which extends to the valve body of a front valve 208, and thence through line 312 to connection 182 at the front servo. In neutral position, this passage is deprived of oil since the land 252 closes the port connected to line pressure conduit 310, the only supply line for line 311. I

' The hereinbefore described hydraulic circuits condition the apparatus for neutral operation in that the front servo, which is fluid pressure applied and spring pressure released, has no oil supplied thereto and, hence, is in released condition due to spring action, as described in connection with Fig. 7. The front clutch is in released or exhausted condition in the manner previously described. The rear servo, which is spring applied and fluid released, has fluid supplied thereto as before pointed out, to cause a release of the rear band 57. The rear clutch is also released or exhausted, as before described, so that in each of the two driving units made up of the two planetaries, no parts of either ofler reaction to other parts and, therefore, there is no transfer of torque or power through these two units. While the description just completed has been devoted principally to the upper transmission mechanism, similar circuits are provided for the lower transmission mechanism which is also conditioned for neutral simultaneously.

, In the operation of this particular invention, it is contemplated that the operator, before shifting the manual valve to eitherdriving range'or low range,-will determine whether it is preferable to operate the mechanism 1 with the final drive unit either in reduction ratio or in direct drive. If the load on the vehicle is extremely heavy, requiring high starting torque, or if the vehicle must traverse a relatively heavy grade, the operator will in all probabilities elect to utilize the reduction ratio of the last unit. It will be noted by reference to Figs. 5 and 11 that the selector valve, having land 126 thereon, is capable of assuming either one of three positions as deterrnined by the spring prmsed ball 124 engaging selectively one of the detent grooves 122. 11f the central groove is so engaged, land 126 will effectivelyclose the opening 116 connected to the passage 117, in which event fluid under pressure from the pump into the chamber 118 and under pressure from the accumulator is arrested at this land. If the lower groove 122 is engaged by the ball, the land 126 ,will be in the position shown in Figs. 5 and 11; in which position the fluid under pressure, both from the pump and the accumulator, will pass from the passage: way 117 into the bore of the valve and out through line to the direct clutch made up of clutch plates 90 and 92. If the upper indentation 122 be engaged by the ball, the land 126will be moved to a downward position permitting the fluid from passage 117 to leave the casing through line to the reduction cone clutch made up of the parts 96, 97 and 98.

First forward range, first gear to effectuate that condition, election may be made as operating the vehicle either in first or second forward range. Let it be assumed that first forward range is selected. The manual valve 200 is moved to the position shown in Figs. 8 and 11. Such movement deprives line 304 of pump line pressure previously supplied through the branch 302 from the line 301. At the same time, the pump supply line 310 is opened and, in addition, supply line 301 is opened. Fluid under line pressure from the pump is supplied through the line 310 to the manual valve, thence through line 311 to the front valve 208, now held open by the end of the manual valve, and through a passage in the body of this valve to the line 312 which leads directly to connection 182 at the front servo, applying pressure to piston 172, which pressure is suflicient to overcome the resistance of the springs in the servo and to force the rod 171 outwardly from the servo to apply the band 42 about the drum surface 41. This action locks the sun gear 37 against rotation. Simultaneously, the fluid previously described asacting to release the rear servo, isexhausted from the outlet 166 and branch 167 through line 304 to the manual valve body and thence through line 308, which is connected by branch line 309 to exhaust at the shift valve 215 (Fig. 9). Exhaust of this fluid from the rear servo permits the springs therein to apply pressure to lockthe rear band 57 about the surface 56 of drum 55, which action locks ring gear 54 against rotation. The front clutch is still exhausted or released, as described in connection with the neutral condition, and the same is true of the rear clutch.

The two drive units comprising the upper mechanism are nowin condition for first speed operation in that each unit is in reduction with their bands applied and their clutches released. However, since the engine is still operating at idling speed, very little drive or transmission of power takes place since, as before described, the turbine 22 is stationary due to the relatively small oil circulation through the fluid coupling, which circulation is retarded by the plurality of plungers 102. It will be understood that the lower unit is conditioned for first speed operation simultaneously with the conditioning of the upper unit so that both mechanisms are now ready for the transmis sion of driving force. The two manual valves of the two mechanisms may be connected for simultaneous sliding through the agency of suitable mechanical linkage where- I by movement of a single member will cause an equal and similar movement of the two manual valves. This particular linkage forms no part of the invention and hence has not been illustrated. Such action is accomplished by accelerating the engine. As soon as the engine and, consequently, the coupling pump 21 reach a predetermined rate of rotation, centrifugal force causes the plungers 102 to move outwardly, clearing the pump passages for the circulation of fluid in the usual manner. When the turbine 22 tries to rotate it transmits torque to the carrier 24, the planets of which engage the sun gear 25 and the ring gear 28. The vehicle being stationary, these latter two gears, due to their connection through the upper and lower mechanisms with the propeller shaft are stationary and offer mutual reaction to the carrier and its planets and the coupling turbine. Asthevehicle starts to move the two gears 25 and 28 will rotate at a rate dependent on the ratio of gearing 30, 31 and 32 and gearing 80, 81

and 8t), and carrier 24 and turbine 22 will move in the same sense as the coupling pump 21. Rotation of sun gear 25 causes rotation of ring gear 27 through the stepped shaft 26. Since sun gear 37 is grounded or locked against rotation by the front band 42, it follows that rotation of ring gear 27 causes rotation of carrier and, consequently, rotation of sun gear 59 of the sec- 0nd unit connected to the carrier 35 of the shaft 36. Ring gear 54, being grounded or locked against rotation by the rear band 57, rotation of sun gear 59 will cause rotation of carrier 64 and, consequently, output shaft 65 of the upper mechanism. Gear is attached to this output shaft and therefore rotates at the same speed. The reverse unit is idling during this operation. Since each of the two planetary drive units in the upper mechanism has one of its components grounded or locked against rotation, the result is drive at a reduction ratio through each unit with an end result of compound reduction. This is the highest reduction ratio possible with the mechanism and creates the lowest output shaft speed in relation to input speed possible with the compound gearing.

At the same time the upper mechanism is put into operation, as just described, the lower mechanism is likevn'se affected by rotation of the ring gear 28 which, through sleeve shaft 29, rotates gear 30, idler 31 and gear 32, connected by the stepped shaft 26 t0 the ring gear 27. Since the lower mechanism is identical in construction with the upper mechanism, it follows that the output shaft 65 is also caused to rotate, but at a different speed of rotation from the shaft 65. The difference in rotative speeds of these two shafts is caused by theditference in number of teeth of gears 89 and 80, which difference is predetermined to obtain the best results. Since idlers are provided in both the front and rear gearing, it follows that the parts of the upper and lower mechanisms rotate in the same direction, which makes possible utilization of servos and bands of the same construction. It will be obvious, however, that the idlers could be omitted if desired, in which event the two output shafts would rotate in opposite directions, which would necessitate slight changes in' various parts of the mechanisms.

If the operator has elected to utilize reduction ratio in the final unit, the selector valve associated with this unit will have been operated to cause engagement of the uppermost groove 122 with the ball 124 as the result of which, fluid supplied both by the accumulator 146 and the pump to chamber 118, as previously described, will pass through the passage 117 into the bore of the valve and out through pipe 120 to operate the reduction cone by forcing the piston 99 to the right (Fig. l), which grounds the cone 96 against the surface 97. Output shaft 65' rotates sun gear which in turn rotates the planets of carrier 86 and, due to grounding of ring gear 88 in the mmner just described, rotation of these planets causes rotation of the carrier 86 at a reduced speed relative to shaft 65'. Carrier '36 is connected directly to 12 propeller shaft 87 and, therefore, imparts rotation to this shaft which extends to the axle of other driving parts of the vehicle.

Should conditions be such as to warrant operation of the final unit in direct drive instead of in reduction ratio, the selector valve 121 would be moved to its other extremity, in which event the fluid supply through passage 117 would exit from the valve bore through line 115 which extends to supply fluid to piston 94 which, when operated, locks the plates 90 and 92 together, thereby locking ring gear 88 and sun gear 85 together. Under these conditions, rotation of the ring gear causes rotation of carrier 85 without any relative rotation of the planets thereof, so that the carrier 86 and propeller shaft 87 rotate at the same rate of speed as output shaft 65'.

When the two output shafts '65 and 65 have rotation imparted thereto, the two governors connected and driven respectively thereby are also rotated so that fiuid under G-l pressure passes through line 235 into the shift valve body of Fig. 9 into contact with the governor plug 210. A branch 260 from line 235 supplies fluid under G-l pressure to the right end of the enlarged part of shift valve 215. Another branch 2611 leads to a reverse blocker 262, the piston 264 of which is moved by this fluid to cause an intercngagement of parts of the manual selector mechanism in such fashion that, when the fluid under pressure reaches a value representative of a relatively low vehicle speed, the manual mechanism cannot be operated to place the transmission mechanisms in reverse position. This type of reverse blocker is well known to the art and requires no detailed description. Branch 189 from line 235 leads to the front servo to operate valve 186 under certain conditions to be detailed later.

The governors also build up G2 pressure but at a slower rate, and the manner in which G-2 pressure is utilized will be explained later.

Line 235', having C-l pressure therein from the governor of the lower mechanism, also has a branch 265 which extends to the reduction lock 266 associated with the manual valve controlling operation of the final unit. When the pressure in line 265 reaches a predetermined value, piston 267 in the lock is moved to the right (Fig. 11), eventually forcing a plunger 263 outwardly into the path of movement of the crank 128 so that change of position of this crank is prevented. In this manner, a shift from direct drive in the final unit to reduction drive is prevented above a predetermined vehicle speed.

As the engine throttle is opened beyond idle, the throttle extension 285 moves valve member 202 to the left (Fig. 8), placing spring 233 under compression, which tends to move the valve 201 also to the left. Oil under pump pressure is delivered by passage 320 from the bore of the manual valve 290 to the bore in which valve 201 slides. Movement of member 201, under the impetus of spring 264, causes the left-hand land of memher 261 to uncover the right-most port connected to the passage 221. This movement admits oil into passage 221, some of which enters the intermediate port connected to line 221 to act against the left-hand end of the land just mentioned. Oil from line 221 also enters the left-most part connected thereto to bear against the main stem part of member 221. As the pressure head of oil in line 221 and the parts of the transmission connected thereto increases to a pressure greater than the force exerted by the spring 204, it will force the left-most land of member 201, and consequently this-member, to the right against the spring sufliciently to uncover the leftmost port so that oil can be exhausted through the passage thus indicated. As the member 202 is moved further to the left, the force of spring 204 moving member 261 to the left is increased, with the result that the pressure head developed in line 221 and its connected parts increases in proportion. This arrangement constitutes the Well-known throttle valve device which operates to provide fluid under regulated pressure proportional to or in dotted lines, Fig. 9) which leads to a channel 401 extending to a bore 402 in which is slidably vmounted a tubular valve member 404. The valve member is made by drilling out solid stock to provide a cup-like cavity in the left end to retain a spring 405, and a second cavity in the right end which is provided with a through-diametric opening 406. Diametrically opposite parts of the lefthand cup wall are provided with slots 407. When oil enters the passage 400 and is directed against the righthand end of the valve, this valve is moved to the left to compress spring 405 and to align the through-opening 406 with internal channels leading to the rear of the regulator plugs 218 and 219 and to the larger part of plug 217. When the throttle valve pressure is sufficiently high, plug 218 moves to therightpopening passage 408 to permit modulated throttle valve pressure to be applied to the rear of the large end of shift valve 215. Likewise, when plug 219 has been moved to the right by TV pressure, passage 409 is opened to permit modulated throttle valve pressure to be brought into play against the large end of the shift valve 216. Pressure'against the larger area of plug '217 moves it also to the right, per- 14 Oil delivered to the top of land 135 serves to move the valve against the resistance of spring 133 until, under predetermined pressure, the valve is moved to such an extent thatoil can be returned to the inlet .of the pump through line 129 connectedto inlet line 279. Thespring 133 is of a strength to cause this valve to act as a regulator, holding the output of the pump to a value of, for

example, from 105 to 115 lbs. per square inch. The output of the pump also passes through channel 152 to the valve 148 and, when the rear pump pressure exceeds the front pump pressure delivered through line 151, the valve 148 is opened, permitting the oil from the rear pump to flow to the front pump and, in some conditions, to take over the work of the front pump in supplying the-hydraulic mechanism. Oil entering chamber 147 also passes through valve 141 to the accumulator and to channel 117 for use in operating the pistons of the final unit.

Shift from first to second When the output shaft 65 of the top unit has attained a plug 210 will move this plug to the left until the land on mitting regulated modulated oil pressure through channel 410 to be applied to the large end of shift valve 214.

The effect of such pressure will be clarified in the later description of the operation of the device.

Oil under throttle valve control is also supplied through line 222 to the left of compensator valve 206. Oil supplied to the bore of the throttle valve 201 is also delivered to the compensator valve 206 and the plug 269, appearing at the right end of the compensator valve; Oil under throttle valve pressure moves the compensator valve to the right while oil under pump pressure movesthe plug 269 in the same direction until arrested by the stop 270. Such movements as shown in Fig. 8 permit oil to pass through the bore of the compensator valve'to line 271 which extends to the connection 168 at therear servo and which has .a branch 272 which extendsto connection 180 at the front servo. Bypass 274 in the manual valve body routes oil to the right of the. plug 269 to exert-pres-, sure to move this plug and, consequently, the compensator valve to the left; This Iarrangement is conven tional for obtaining regulated compensator fluid responsive to variation's in throttle valve pressure. H r

their respective drums for locking the same against rotation. As before mentioned-the rear servo is spring applied and oil released so that it becomes desirable to assist the springs in applying the rearband as torqueis increased. This additional oil obviates the necessity of-increasing the size of the servo and its springs should spring actionalone be employed. The fluid undercompensator' control introduced into thefront servo acts on the piston 175 to assist the pressure acting on piston 172 in moving the rod 171 outwardly into band-engaging position. Thus it will be seen that, as the engine is accelerated with the transmission in first speed, force to lock the two bands is increased proportional tov the throttle opening.

The lower mechanism also operates to drive two additional pumps. One of these pumps 275 serves to scavenge oil from the final unit sump by line 276 and to return it to the transmission sump through line 277. The other pump 278 draws oil from the transmission sump through line 279 connected to supply line SL and delivers it through line 280 to the connection 130 in the valve body the shift plug 214 clears the port connected with the passage 256 in the valve body. Oil under pump pressure supplied to passage 256 by line 255 then flows through an internal passage in the shift valve body to the line 316 which extends to the double transition valve 207, from which the oil passes through line 315 and connection 181 to the front servo and through branch 314 to the front clutch. The oil reaching the front servo acts on-piston 172 and, through the passage in rod 171, also acts on piston 174 to move the rod 171 inwardly torelease the front band 42. Oil is still being supplied to the other surface of piston 172 and is being supplied from the com pensator valve against piston 175, but the piston areas are such that these release pressures and the springs will overcome both apply pressures. This action retains bandapply pressure available, for use but overbalanced by band-releasepressure and spring action. Simultaneously, thefront clutchis actuated to lock the plates 39 and 44 together, which locks the planets of carrier 35 to' the sun, gear 37 of the front driving unit in the upper mechanism:

Since these gears are locked together, it follows that rotation of the ring gear 27 causes rotation of the planets andsungea r ,37 at the same rate or, in other Words, the front unit operates in direct drive. Status of the rear unit re mains unchanged so that the output shaft 65 'is driven by the carrier of the rear unit as before, but with the single.

of the upper unit must rotate at a higher rate than the,

output shaft of the lower mechanism, even though these two mechanisms are in the same speed ratio condition. Consequently, since changing of gear ratio takes place in response to vehicle speed, as represented by the speed of rotation of the output shafts, and torque demand, as represented by throttle valve pressure, the upper unit will shift from first to second gear ratio while the lower mechanism will remain in first gear ratio. 'Due to the geared connections between the output shafts, the change in gear ratio in the upper mechanism causes a change in the speed of rotation of the ring gear 27 and, consequently, of the sun gear 25 of the differential planetary unit. Since this planetary can operate to provide differential drive, it will be seen that the input to the upper unit has its speed properly varied to accommodate the upper mechanism for 15 operation in second gear, while the lower mechanismis still operated in first gear.

As the speed of rotation of the lower output shaft 65' increases, a point will be reached at which torque demand and vehicle speed will cause this lower mechanism also to shift into its second gear ratio, which shift is accomplished in exactly the same manner as just described in association with the upper mechanism.

Shift from second to third As the speed of rotation of the two output shafts, 65 and 65, increases with the same relative differences maintained, the G-1 pressure from the governor of the upper mechanism will reach a value of such magnitude that, when applied to the large area of the 2nd to 3rd shift valve 215 through the line 260 combined with G-2 pressure from the same governor applied to the regulator plug 211, the pressures will cause a shift from second to third gear ratio in the upper mechanism. The 6-2 pressure is supplied by line 238 from the governor and branched to lead both to the regulator plug 211 and to the right end of the shift valve 215. These two governor pressures, at a proper time, will combine to exceed the throttle valve pressure acting on the regulator plug 218, modulated throttle valve pressure on the valve 215, and also the strength of the springs acting on the large area of the shift valve. When this occurs, valve 215 is moved to the left. The rear clutch, which was previously released or exhausted, now becomes closed by oil under pump pressure from line 301 to the manual valve bore, then line 306 therefrom to the branch 307 leading to the shift valve body, the bore of the second to third shift valve and therefrom through the line 309 to the rear clutch. At this point the oil acts on piston 60, compressing plates 52 and 59 against the buttress 62, so that, when the clutch is fully engaged, the sun gear 50 is elfectively locked to the ring gear 54. Simultaneously, oil leaving the shift valve body through line 309 progresses through line 308 to the bore of the manual valve body and thence through line 304 and the conduits'166 and 167 at the rear servo. Oil from these conduits acts on the two pistons 158 and 162 to move the rod 157 inwardly of the servo thereby to release band 57 from drum surface 56. Oil flowing through line 304 is partially diverted to branch 305 to the right end of the double transition valve 207. Since the area of the valve 207, against which oil from line 305 impinges, is larger than the area subject to pressure from the line 274, it follows that the valve 207 is moved to the left until the port communicating with line 316 is closed and a port communicating with line 340 is opened. Closing of the port leading to line 316 cuts off the supply of fluid through lines 315 and 314,"which caused the release of" the front band and the closing of the front clutch, respectively. Opening of the port connected to line 340 permits these devices to be exhausted through branch 314, line 315, the bore of the double transition valve, and line 340 to exhaust at the bore of the shift valve 216. When the band-apply pressure of oil is exhausted through the line 315 from the front servo, this device is immediately actuated to apply the front band, since the supply of fluid thereto through line 312 had been maintained during operation of the mechanism in second speed ratio. However, if the pressure of fluid from the governor, i.e., G-l pressure, supplied to the valve 186 in the front servo through line 189 is sufficiently high to move this valve in its bore, the reapplication of the front band will be somewhat retarded since oil for that purpose must pass through the restriction 188 in valve 186. This prevents the band being applied in too abrupt fashion since, in the shift from second to third, a double transition takes place. In other words, a transition takes place both in the front unit and in the rear unit of the upper mechanism. The front unit is shifted from direct drive to reduction drive, while the rear unit is shifted from reduction drive to direct drive. Thus it will be seen that the transmissionof power through the two units is as follows: the band 42 being applied, sun gear 37 is locked against rotation so that rotation of ring gear 27 causes rotation of the planets of the carrier 35 and also rotation of this carrier at a reduced rate. Such rotation is imparted directly to the sungear 50 of the second unit and, since it is in effect locked to the ring gear 54 by the rear clutch, the carrier 64 must, of necessity, rotate therewith. Third speed, therefore, represents reduction drive in the front unit and direct drive in the rear unit.

It will be understood that the change in gear ratio in the upper mechanism from second to third occurs while the lower mechanism remains in second gear. However, as soon as the vehicle speed increases to the proper degree, the lower mechanism will also shift into third speed ratio so that both mechanisms for a time will be in the same condition.

Shift from third to fourth When the. vehicle speed is increased sufiiciently, the second regulating valve in the governor will supply G-2 oil pressure through the line 238 and a branch 231 to the large area of the 3rd to 4th shift valve 216 and also through a branch 282 to the outer end of the governor plug 212. When the pressure so supplied is sufficient to overcome the spring acting on the shift valve as augmented by throttle valve pressure and modulated throttle valve pressure, the shift valve 216 will be moved to the left to uncover a port connected to the branch 321 connected to the line 306 which derives oil from the pump 33. Uncovering of this port permits oil under line pressure, and supplied by branch 321, to traverse line 340 to the double transition valve and from the bore of that valve through the line 315 and branch 314 again to release the front band and simultaneously apply the front clutch. This action is identical with that described in connection with the shift from first to second. The rear servo and the rear clutch remain in the condition established for third speed operation.

In this fourth speed ratio of the upper mechanism it will be found that the front unit thereof is in direct drive and that the rear unit also is in direct drive so that the output shaft 65 rotates at the same speed as the input ring gear 27. Y

The shift from third to fourth, taking place in the upper mechanism, occurs while the lower mechanism is still in' third speed condition but, as the vehicle speed increases, eventually the lower mechanism likewise will automatically shift to fourth speed condition, following which the transmission will continue operating with the two mechanisms in the same condition but with the upper mechanism rotating at a faster rate than the lower mechanism. Such difference is permitted by the differential drive. afforded by the planetary unit operated by the coupling device.

In this particular transmission which, as before mentioned, is intended for heavy duty service, the controls have been arranged so that, should the vehicle speed drop below that required to sustain operation in any particular gear ratio, the drop in governor pressure caused by the retarding of vehicle speed will reduce the pressure applied to the governor plugs in such manner that spring pressure and throttle valve pressure opposing governor pressure can overcome governor pressure and automatically down-shift one of the mechanisms to the next lower ratio. For example, if both'mechanisms are in fourth speed ratio and the vehicle speed drops, the first effect will be a decrease in governor pressure to the 3rd to 4th governor plug 212' (not shown) so that the 3rd to 4th shift valve 216" will be moved to its extreme right-hand position by spring pressure and throttle valve pressure acting on the plug 219, and modulated throttle valve pressure acting on the left-hand end of the shift plug. This will restore the lower mechanism automatically to third speed condition, causing the planetaries to be actuated for that purpose. It will be obvious that further de creasein vehicle speed will cause progressive downward shifting of the two mechanisms at staggered intervals in the direct reverse order of their up-shifting. It Wlll also be evident that the down-shifting can occur at any speed ratio established for the entire transmission. While the description of the operation of the mecha- Overall Upper Lower Transmission Mechanism Mechanism 1st; 1st 1st 2nd 2nd 1st 3rd 2nd 2nd 4th 3rd 2nd 6th 3rd 3rd 6th 4th 3rd 7th 4th 4th From this table it will be seen that two parallel four speed mechanisms, having their inputs differentially 'driven and having their outputs maintained at a predetermined different speed ratio, will provide an overall transmission having seven speed ratio changes possible therein.

In the operation of heavy vehicles, the negotiation of heavy upgrades or downgrades may make it desirable to limit the transmission to operation in any gear ratio. When such conditions are present, the operator moves the manual valve to the right to register with the second forward position shown in Fig. 8. ,Ihis movement causes the land 252 to uncover, at least partially, a port leading to line 330. This'line extends to the regulator plug 218, associated with the 2nd to 3rd shift valve and through a branch 331 to the throttle valve auxiliary located in the shift valve body. In this condition oil from the pump 33 is supplied by the line 301 and branch 310 thereof to the bore of the manual valve and therefrom through the line 330 and branch 331 to cause the application of full line pressure to the regulator plug 218 and to the plugs 217 and 219. Since the plug 218 has differential areas, the oil entering through line 330 will act on the larger area and move this plug to the right. At the same time, oil, entering the body through line 331, passes through one or more of the slots 407 in the valve 404, aiding spring 405 in moving this valve to the right. Such movement of the valve 404 to the right permits oil to pass through the diametrically opposite slots in the lefthand cup and through channels shown to act on all three regulator plugs. Full line pressure having been applied to these three plugs and also modulated full line pressure applied to the shift valves 214, 215 and 216 through the channels 410, 408 and 409 respectively, it follows that extremely high governor pressure would'be necessary to move these shift valves to the left.

The valve body springs, valve areas, and pressures are so arranged and controlled that, in this second forward drive position, the upshifts will occur if and when the vehicle has attained a speed which makes the engine run a little faster than the normal no-load-speed setting of the engine speed governor. This driving range is particularly advantageous for ascending steep grades or for utilizing the engine as a brake in descending grades.

.Reverse To operate the mechanism for reverse drive it is necessary to move the manual valve 200 to the R position of Fig. 8. Such movement providesoil underline pressure from pump 33 through the line 301, branch 310,

to the bore of the manual valve from which it exits through the line 350'to the reverse unit, atwhich point it is directed to act against piston 74 thereof, causing this piston to clamp cone 71 to the grounded cone 72. Branch line 352 from line 350 extends to the control piston of pump 33, actuating it to increase the pressure output of the pump. As the result of this interaction, the pressure of the oil supplied to piston 74 is increased to approximately double the pressure normally supplied by the pump during forward operation of the transmission. Oil supplied to the bore of the manual valve through the branch 310 also passes therefrom through line 311 to the valve body of front valve 208 to exit therefrom, under suitable conditions, through the line .312 which, as before explained, extends to the front servo to cause it to apply the band 42 to drum 41 of the front driving unit. The front clutch is exhausted through branch 314 joining line 315, which extends to the double transition valve and therefrom through line 316 to exhaust at the shift valve 214.

In reverse it is necessary that the rear band be released and the rear clutch exhausted. To accomplish the former, line pressure is supplied through conduit 301, branch 302, to the bore of the manual valve, and therefrom through line 304 to the rear servo, actuating the same to release the band in the manner previously described. The rear clutch is exhausted through line 309 to the shift valve 215. 1

The upper mechanism is in condition for driving the vehicle in reverse since the front driving unit is in reduction ratio while the rear band is released and the rear clutch is exhausted and the ring gear of the reverse planetary unit is locked against rotation. The flow of power therefrom extends through the first drive unit in reduction to the sun gear 50 acting upon the planets carried by the carrier 64. Assuming that the vehicle is at rest, this carrier 64 is initially grounded due to the output shaft 65 being connected to the wheels of the vehicle. Rotation of sun gear 50, under this condition, causes the planets of carrier 64 to act as idlers, the rotation of which imparts rotation to ring gear 54 in the opposite direction to that of the sun gear 50. Ring gear 54 drives sun gear 68 of the reverse planetary unit in this reverse direction and, since the ring gear thereof is held against rotation, the carrier 69 and its planets must rotate in the same direction as the ring gear 68. Planet 69 is connected directly to the output shaft 65 so that rotation of this carrier in reverse direction causes rotation of the output shaft also in the reverse direction. This reverse rotation is immediately imparted to the planet 64, with the end result that the output shaft continues reverse rotation at a reduced rate. It will be seen that the reduction obtained in the first drive unit is added to that obtained in the reverse unit for an overall reduction higher than that employed in forward drive.

Since a greatly increased oil pressure is utilized for assuring locking of the reverse cone 71 which is accomplished by action of the variable capacity pump 33, which in turn supplies fluid also to the front band, it is advisable to prevent this increased pressure from acting on the front servo and, therefore, use is made of the front valve 208 arrangement. Referring to Fig. 8, it will be seen that oil, entering the valve casing through line 311, passes through a channel into a space between land 370 and land 371 of valve 208. It also can pass around the lower end of the land 371 into the interior thereof in which is located spring 372. Fig. 8 shows the position of this front valve in both normal driving range and in low range and, due to the contact of the upper end of wardly until the land 370 is arrested against further "movement. The pointed endof the manual valve makes -370 has moved the valve downwardly sufiiciently to open the port leading to outlet line 312. When the reaction in line 312 reaches a point at which the pressure, so developed, can co-act with spring 372 toclose this port, further increased servo pressure is prevented. The valve 208 therefore acts as a regulator to permit supply of oil to the front servo at approximately half the increased 'pump pressure, thereby preventing damage to the front band and its associated mechanism, which might result from; exceedingly high servo oil pressure.

With the two mechanisms operating as described in connection with First Forward Range, and with the *final unit in'reduction, it will be apparent that the vehicle speed can be increased to the maximum possible with the particular engine employed. However, further increase in vehicle speed can be obtained by shifting the final unitfro'm reduction drive to direct drive.

The exactmanual controls for accomplishing this change have not been shown, but it will be apparent that any type of control can be used, preferably one in which it is necessary to simultaneously move the controls for the two mechanisms into neutral position before the disengagement of the reduction drive cone clutch or the direct drive plate clutch in the final unit and engagement of the other unit. In the co-pending application of Carl J. Bock et al., S.N. 210,830, filed February 14, 1951, for

- Heavy Duty Drive Gearing and Control System, now

Patent No. 2,740,303, issued April 3, 1956, disclosure has been made of an automatic transmission having a manually'controlled transmission in series therewith in which linkage between the manually operated shift mechanism and the manual valve of the automatic transmission serves to position the manual valve in neutral whenever the manual transmission is shifted from one gear ratio to another. Similar linkage may be used in the present arrangement wherein the two manual valves are connected together for simultaneous similar motion. Since the two mechanisms must have the control valves of each thereof in neutral position momentarily, it follows that fluid will be exhausted from the shift valves and their associated parts duringthis pause, with the result that only fluid to cause release of the rear band in each mecha- .unit in reduction, a change may be made to activate the final unit in direct drive, as the result of which the speed of rotation of the output shafts will be so reduced that, when these mechanisms are again operated to transmit power, they will begin such transmission in second or third ratios as the gearing may demand. After such reactlvation of the mechanisms, the advance through the range of gear ratios will be continued in the manner previously described until these mechanisms again reach a condition establishing 7th speed.

The transmission, hereinbefore described as embodying one form of this invention; provides a wide range transmission for trucks, buses, and other heavy duty vehicles.

This transmission incorporates improvements in operation such as, for example, continued acceleration throughout a' range of gear shifts due to the application of force sep rately and differentially to the two mechanisms fro ma single source of motive power. The parts of the planetary differential gearing connected respectively to'the two mechanisms offer mutual reaction and, consequently, so long as each thereof continues its reaction to the other substantially uninterruptedly, the transmission of power from the engine to the propeller shaft will be of a continuous nature. Therefore, if the shifts in the two mechanisms are accomplished cleanly and without appreciable lag, the mutual reaction will be maintained so that acceleration of thevehicle can be made substantially continuous. Another advantage resides in the fact that, with this continuous acceleration, there is very little drop in engine speed during any particular shift in either mechanism so that the engine, particularly a diesel engine, can be operated at its maximum efficiency through the range of shifting.

This invention also makes provision for utilizing the engine and transmission for power purposes while the vehicle is at rest. To accomplish such purpose, the valve 126 can be moved to its intermediate position, blocking the port 116, so that oil from the reservoir or from the pumps cannot continue either to the reduction cone actuator of the final unit or to the direct clutch thereof. Under this condition, it will be obvious that the propeller shaft 87 has no motion of any kind imparted thereto. Consequently, a power take-off shaft can be connected to the idler gear 81 between gears and 80' so that, when the engine and the mechanismms are operated, this gear train will also operate and the take-off can be used to drive any desired piece of machinery.

While the invention has been described in connection with two mechanisms driven through the agency of a fluid coupling, it will be apparent that other types of well-known mechanisms can be employed in this fashion. By reference to Fig. 12 of the drawings, it will be seen that two types of mechanisms, indicated by blocks A and B, can be operated in parallelism. The mechanisms may be of any well-known type; for example, the type utilizing a hydrodynamic torque converter and gearing, or another type employing a fluid coupling intermediate the two planetary units of a compound transmission such as are shown in US. Patents Nos. 2,176,138; 2,211,233; 2,377,696; or the pending applications of Walter B. Hern don, S.N. 199,806, filed December 8, 1950, for Transmission and Fluid Pressure Control, now Patent No. 2,763,162, issued September 18, 1956; and SN. 235,213, filed July 5, 1951, for Transmission Control System, now Patent No. 2,790,327, issued April 30, 1957; or the mechanisms may be of any well-known automatic type, or even semi-automatic type. In the particular arrangement shown in Fig. 12, it will be seen that the output shaft 500 of the engine, indicated by the block E, serves to drive the bevel gear spider or carrier 501, on the outer portions of which are mounted planet bevel gears 502. Shaft 503, at the right of the spider 501, is attached to crown gear 504 meshing with gears 502, and to gear 505 meshing with gear 506 on the input shaft 507 of mechanism A. The opposing crown gear 508 is attached to the drum member 509 and also to sleeve 510 and pinion 511, which drives gear 512 on the input shaft 514 of mechanism B.

The output shafts 515 and 516 of the respective units are connected by gearing 517, 518 and 519 to the propeller shaft 520. Of course, a final reduction-direct drive unit 521, such as that previously described, can be employed as desired.

In this arrangement, it will be evident that the inputs of the two mechanisms are differentially driven by the engine E, while the outputs are connected in any desired gear ratio so that these mechanisms, if of automatic shift type, can function in the same manner as the mechanisms of Figs. 1 to 11 inclusive.

Furthermore, it will be obvious that theinvention is not' limited to the employment of two mechanisms in parallel, but can be extended to include as many mecha- -21 iiisins, operatingsequentially, as can beaccommodated by available space and as maybe required by existing conditions.

A manner in which the increase in mechanisms can be accomplished will become more evident by reference to Figs. 13 to 16 inclusive. Referring to Fig. 13, the engine indicated by the block E has a drive shaft 600connected to a planet carrier 601 having planets 602 in mesh with a sun gear 604 and a ring gear 605. Sun gear'604 is secured to shaft 620 which constitutes the input shaft for mechanism A which may be of any of the types either described in detail or in general terms. The ring gear 605 isconnected to a pinion 606, which drives shaft 621, through the idler gear 607 and the gear 608 secured to shaft 621. Shaft 621 constitutes the input shaft for the mechanism B. Mechanism A has an output shaft 630 with gear 631 driven thereby, while mechanism B has an output shaft 632 with gear 634 driven thereby. Gears 631 and 634 mesh with gear 635 to drive the same and this latter gear may be secured to the propeller shaft 636. With this arrangement, due to the interposition of the idler gear 607 in the input to mechanism B and the idler gear 635 connected to the output shaft of the two mechanisms, it follows that, the input shafts of the two mechanisms rotate in the same direction and the output shafts thereof also rotate in the same direction. While the propeller shaft 636 has been shown as being driven by the idler gear 635, it is obvious that the propeller shaft can be driven directly by either of the other gears 631 or 634. Furthermore, a final reduction-direct drive unit may be added to the propeller shaft if desired.

Referring to Fig. 14, again we find the engine illustrated by block E driving a shaft 700 which is connected to carrier 701 carrying the planets 702 in mesh with a sun gear 704 and a ring gear 705. The sun gear 704 is fastened to and drives shaft 720, which constitutes the input shaft for mechanism A. However, the ring gear 705 in this form is-connected to a carrier 709 for planets 710 which mesh with a sun gear 711 and a ring gear 712. Sun gear 711 is on one end of a sleeve shaft 714, the

other end of which carries a pinion 715 driving a gear 716 through idler gear 717. Gear 716 is secured to and drives shaft 721 which constitutes the input shaft of the mechanism B.

Ring gear 712 has connected thereto a sleeve 750 and a pinion 751 driving gear 752 through the idler gear 754. Gear 752 is connected and drives shaft 755 which constitutes the input shaft for mechanism C. These three mechanisms have output shafts 730, 732 and 760, which are connected to drive gears 731, 734 and 761, respectively, with interposed idler gears 762 and 764. The gear 731 serves to drive the propeller shaft 736, which shaft may be integral with output shaft 730 if desired.

With this arrangement it will be seen that three mechanisms of the type previously described are operated in parallel with their inputs differentially driven by the planetary gear arrangements and with their outputs connected together in a predetermined speed relation. Due to the employment of the idler gears in the gear trains associated with the input shafts of mechanisms B and C, the input shafts of these mechanisms will rotate in the same direction as the input shaft of mechanism A. The employment of the idler gears in the train connecting the output shafts also assures that these output shafts will rotate in the same direction. Again, as in Fig. 13, the propeller shaft may be driven by any one of the gears in the train.

Referring to Fig. 15, an engine indicated by the block E has drive shaft 800 driving a planet carrier 801 having planets 802 meshing with the sun gear 804 and ring gear 805. The sun gear 804 is secured to and drives shaft 820 which constitutes the input shaft for mechanism A. Ring gear 805 is connected and drives a pinion 806. Up to this point the arrangement is similar to that described in Fig. 13, but it will be noted that the pinion 806 is in .22 direct meshwith gear. 808, connected to and.driving shaft 821, which constitutes the input shaft of mechanism B. Since the idler gear employed in association with the input shaft of mechanism B in Fig. 13 has been omitted, it follows that the input shaft 821 rotates in the opposite direction to shaft 820. Furthermore, the output shafts 830 and 832 have gears 831 and 834 connected to them, respectively, and in mesh with each other. Thus, the two output shafts 830 and 832 also rotate in opposite direction, in conformity with the input shafts. The propeller shaft 836 can be driven by either of the output gears.

Fig. 16 illustrates the manner in which three mechanisms can be employed utilizing the principle demonstrated in Fig. 15. In Fig. 16 the engine E has a drive shaft 900 driving the carrier 901 for the planets 902 in mesh with sun gear 904 and ring gear 905. Sun gear 904 again drives input shaft 920 for mechanism A while ring gear 905 drives a secondcarrier 909 for planets 910 in mesh with sun gear 911 and ring gear 912. Sun gear 911 is on one end of sleeve shaft 914, the other end ,of which has pinion 915 thereon which is in direct mesh with gear 916 attached to the input shaft 921 of mechanism B. The ring gear 912 has an extension 950 supporting gear 951 directly in mesh with gear 952 on the input shaft 955 of mechanism C. These three mecha nisms have output shafts 930, 932 and 960, having gears 931, 934 and 961 attached thereto, respectively. The gears constitute a train similar to the train of Fig. 14, but with the idler gears omitted.

Since the idler gears have been omitted from the drive trains associated with the inputs of mechanisms B and C and also have been omitted from the output gear train, it follows that the input shafts of mechanisms B and C will rotate in the opposite direction to the input shaft of mechanism A, and the same is true of the output shafts. Again, the propeller shaft 936 may be driven by any one of the output shafts.

By comparing Figs. 13 and 14 and Figs. 15 and 16, it will be seen that the addition of other mechanisms would involve no more than the provision of an additional seriated planetary gear arrangement for each mechanism employed.

In some of the transmissions well known to the art and particularly in some of those described in the identified patents and patent applications, use is made of a fluid coupling interposed between two forward drive planetary gear arrangements, due to which, in some speed conditions such as in third and fourth speeds, divided torque paths are established between the input of the transmission and the output thereof. Consequently, when two or more of these transmission mechanisms are employed in the present invention, it follows that in some speed ratios of the entire transmission the mechanisms will have incorporated therein a number of torque paths in excess of the number of transmissions.

In the practice of this invention, regardless of the mechanism used therein, it is to be understood that the differential gearing connecting the inputs of these mechanisms can be so selected as to divide the torque load between the mechanisms in any suitable proportion. Since the upper mechanism in the detailed description normally rotates at a higher speed than the lower mechanism in the same gear ratio, it may be desirable to cause this upper unit to carry either a higher or a lower proportion of the torque load. On the other hand, it may well be that most advantageous operation of the transmission can be obtained by an equal division of torque load. In either situation it will be evident that the output power used in driving the vehicle is divided between the output shafts of the two mechanisms, with one shaft delivering more power than the other alternately as the mechanisms progress through their pattern of shift change.

While in all of the transmissions illustrated and described the output shafts have been shown as being con- 

